In German Patent No. 39 02 081 a percussion boring machine of this kind is described in which the cutters are arranged on a breaking-up head that is connected to the machine housing by a tension- and compression-resistant universal joint to enable it to follow curves.
Although the cutters that serve to break open the pipeline are thus located in front of the tip of the boring machine, the opening-out cone is located at the back of the housing and permanently connected to it.
The cutters on the breaking-up head can only be changed individually, or else the whole head must be detached from the machine at its universal joint and exchanged. While this kind of breaking-up head can be adapted to old pipes of different diameters, the opening-out cone is permanently connected to the machine housing, so that adaptation to the diameter of the pipe to be drawn in is only possible by the use of a percussion boring machine of corresponding diameter.
Finally the guidance of the machine is also unsatisfactory, particularly as it enters the pipe to be broken up, since the universal joint between the head and the machine allows deviation in all directions, so that an expensive mounting is required to guide the machine. A traction cable through the old pipe is also necessary.